First, the light-emitting mechanism of LED lights source
with incandescent or gas discharge lamp light-emitting principle is very different. LED spontaneous luminescence is due to the compound of electrons and holes.
LED is formed by the P-type semiconductor layer P and N-type semiconductor the formation of the N layer, and into the middle of the double hetero structure active layers. The active layer is a light-emitting area, the use of external power injected electrons to the PN junction under forward bias, the role of the N-zone electronic will is the direction of diffusion into the active layer, P area hole will be the negative direction of diffusion into the active layer, the electron and hole recombination will result in the spontaneous emission of light. As led source used different material, its diode electron, hole-share level different energy level high and low differential photon affect the binding energy of different wavelengths of lights, that is , the different color of light, such as red, orange, yellow, green, blue or is not visible and so on.
Second, the white LED bulbs
The emergence of the white LED provide white LED semiconductor lighting for the growing number of indoor and outdoor lighting project. The white led source luminous efficiency has made substantial progress, the white LED has even begun to challenge the status of the traditional light source.
The white LED has two main ways: The first one is to get white light through the phosphor conversion; second is to put different colors of LED chip package together with multi-chip hybrid white light. For the above two ways, according to the number of light sources in mixed white base color, it can be divided into two primary color system and the multi-primary color system.
Phosphor converted white LED
(1) two color phosphor converted white LED lamps
wo-color white LED is made of blue LED chip and YAG phosphor. Generally use blue chip InGaN chip, and can also use the AlInGaN chip. The advantages of blue-chip LED with YAG phosphor are simple structure, low cost, simple production process, but there are a number of shortcomings, such as blue LED efficiency is not high enough, so resulting in low white led source efficiency. The phosphor itself exist energy loss, and with the aging time of phosphor and packaging materials, it also result in the color temperature drift, and shortened life expectancy.